The present invention relates to a method for bringing about the transformation of a medium such as carbon dioxide or other gases or mixtures thereof into snow.
When using carbon dioxide (CO2) or other gases or mixtures thereof for the purpose of being able effectively to cool surfaces and other spaces of varying size and nature, for example in order to kill harmful insects or other undesirable animals, it is important to be able to achieve a low temperature rapidly and effectively and to minimize the quantity of gas used. Previously disclosed methods, in which existing snow tubes are used, have not proved to be so effective, and an unacceptable cooling effect has accordingly been achieved. See, for example, U.S. Pat. Nos. 4,911,362; 5,027,546 and 5,349,778. In order to cool surfaces and spaces effectively so that harmful insects and other undesirable animals are cooled rapidly to kill them, it is necessary for the largest possible proportion of the gas used to be converted into snow, which, at the time of spraying, exhibits a low temperature, a good adhesive capacity and a high ability to cover the surfaces in question so that the insects are killed effectively.
The principal object of the present invention is thus, in the first instance, to identify a method which effectively solves the aforementioned problems efficiently and simply.
The aforementioned principal object is achieved by means of a method in accordance with the present invention, which is characterized essentially in that, for the purpose of being able effectively to cool surfaces and different spaces of varying size and nature in order to kill harmful insects or other undesirable animals, the aforementioned medium and the snow produced from it are caused to interact with the surfaces of a snow-producing nozzle extending from a discharge orifice for the medium, in that the aforementioned medium, after exiting from the discharge orifice, is permitted either to expand into an elongated space which exhibits a uniform cross section, or to act against a number of obstructions situated along the flow path of the medium as it flows out between the discharge orifice for the medium and an outlet for the formed snow, in conjunction with which the produced carbon dioxide snow is intended for the purpose of animal pest decontamination.
There are no previously disclosed means which permit the aforementioned desired object to be achieved, and use is made of snow tubes, which are seen to be not so effective from the patents referred to above, for example.
U.S. 4413756A presents insect control with snow formed by spraying through spaces whose width, and thus their volume, vary.
EP 0 891 945 A2 presents a snow spray nozzle which is formed by an obstruction in the form of a metal disc. This component is already present at the start of spraying of the medium in liquid form and accordingly only one side of it is in contact with the liquid phase, as distinct from bristles, which thus function in a different way in the snow forming process.
A further object of the present invention is thus also to identify means that are suitable for use in the performance of a method in accordance with the present invention and are intended primarily for use in animal pest decontamination.
The aforementioned further object is achieved by means in accordance with the present invention, which is characterized essentially in that a snow-producing nozzle comprises an orifice for the supply of medium at its inlet end, and in that a subsequent elongated space leading from it exhibits a uniform cross section, or in that a number of obstructions for the medium as it flows through are situated in the interior of the nozzle between the orifice for the discharge of the medium to the nozzle and the snow outlet from the nozzle.